The overall objective of my proposed research is to study solvent accessibility in folded proteins and in the contact region of associating proteins. The principle methods employed will be hydrogen- tritium exchange kinetics and proton nuclear magnetic resonance spectroscopy (NMR). Processes of solvent exposure of buried groups in folded proteins are fundamentally related to the dynamic behavior of native proteins in solution. Such process are not observed in X-ray crystal structures, nor is it expected that they should be. Information about these processes must come from solution methods, of which hydrogen exchange kinetics and NMR are particularly well suited. My proposed research provides a feasible method for study of single peptide NH protons thereby overcoming the major difficulty in interpretation of hydrogen exchange data and most other solvent perturbation spectroscopic data.